<template>
  <div id="vue2about">vue2 about</div>
</template>

<script>
export default {
  mounted() {
    const microDocument = document.getElementById('vue2').firstChild.shadowRoot
    console.log(microDocument.getElementById('vue2about'))
  },
  created() {
    window.a = 2
  }
}
</script>

<style>

</style>